Thermographic copying sheet and heat sensitive composition



April 13, 1965 H. A. WARK 3,178,306

THERMOGRAPHIC COPYING SHEET AND HEAT SENSITIVE COMPOSITION Filed April 12, 1962 Infru- Red Transparent Paper Base INVENTOR Homer Albert Work gm; QMfiE Wm'E ATTORNEYS United States Patent Ofiice 3,178,306 TI-ERMUGRAPHIQ CQPYBNG SHEET AND HEAT ENSITIVE CQMPOSKTIUN Homer Albert War-k, Sannderstown, Rl, assignor, by mesne assignments, to firchard Paper Company, St. Louis, Mo., a corporation of Missouri Filed Apr. 12, 1962, Ser. No. 186,853 16 Claims. (Cl. 11736.8)

This invention relates to heat sensitive materials useful in the preparation of copies of printed or written matter, images, designs, drawings and other graphic material. More particularly, it is concerned with the preparation of thermographic or heat sensitive copying materials such as copying papers or duplicator sheets which may be utilized in the preparation of duplicate copies of printed or other graphic subject matter by exposure to heat, e.g. as infra-red irradiation, without requiring subsequent developing or fixing operations.

Thermographic copying involves intensively irradiating the printed original with radiant energy which is preferentially absorbed and converted into heat energy by the printed or image areas of the original, and utilizing the heat pattern thus formed to bring about a corresponding visible change in the heat-sensitive copying material. The method is adaptable to the reproduction of printed, typewritten, a pencilled material, sketches, and the like. The heat-sensitive copying material can also be used in heated stylus-type recording machines. The heated stylus produces a visible trace on the recording paper.

Heat-sensitive compositions suitable for use in preparing thermographic copying materials are well known in the prior art. However, these compositions all have characteristics which present disadvantages. For example, many compositions are known which are both heat and light-sensitive. If thermographic copies made on sheets sensitized with such compositions are left for a period of time near a window, a uniform coloration will appear, making the image unreadable or barely readable. Some compositions are unstable and will deteriorate even in a dark file to such extent that the image will become unreadable. Some compositions will interact with typewriter-made carbon copies, and papers sensitized with such composition, when filed with carbon copies, are likely to form an image of the carbon copy on the heat-sensitive paper. Some of these compositions require an extremely high temperature, or heating for a relatively long time at a specific temperature, or heating over a wide range of temperatures, to produce a visible image of sufficient intensity to be readily legible. Other compositions are pressure-sensitive and will form coloration showing marks or scratches produced in normal handling. Still others are unstable to premature interaction of their constituents, or are moisture-sensitive, and so have short shelf-life and must be used soon after coating.

It is the primary object of this invention to provide novel heat-sensitive compositions suitable for sensitizing sheets of paper or other material for use in facsimile copying processes or in heated stylus recording machines, which compositions are insensitive to light and moisture but which, when subjected to heat irradiation for a short period over a relatively narrow range of temperature, undergo a visible change of notable intensity. Heatsensitive compositions in accordance with the invention are characterized by good stability, freedom from interaction with typewriter carbon papers, and good shelflife. The invention provides white or colorless heatsensitive compositions that convert to dense black images; thus the final thermocopy has a black image on a white original.

This invention provides thermographic copying materials which have advantages over previously known heatsensitive copying papers in that images resulting from exposure to an original in a suitable thermographic copying apparatus are efiicient ultra-violet radiation absorbers, whereas the original or unaltered heat-sensitive composition is highly transparent to ultra-violet radiation; thus this novel copying paper can be used as a master for making diazo prints in a diazo machine. Further, the images obtained are efiicient absorbers of infra-red radiation, whereas the heat-sensitive compositions to be described are highly transparent to infra-red radiation; thus a print made on a copy sheet manufactured according to this invention can be used as an original for making additional copies on a suitable thermographic copying apparatus.

These advantages are obtained according to the principles of this invention by employing as a heat-sensitive composition an organometal compound dispersed in a film-forming binder coated on a suitable support such as paper or film, which preferably is substantially transparent to infra-red radiation. Additional components may be added to improve the contrast, color or appearance of the heat-sensitive copying sheet. The organometal compounds that are used in practicing this invention are compounds containing sulfur which decompose when heated moderately to form a metal sulfide.

The compounds used for mafing heat-sensitive compositions according to the invention are reaction products of (i) a Grignard-type organometallic compound having the structure (R) -M(X) in which R is a substituent selected from the group consisting of aryl and alkyl radicals, M is a metal of the group consisting of bismuth, chromium, gallium, germanium, iron, lead, mercury, tellurium, and tin, X is any anion substituent (e.g. carboxylate or an inorganic anion), y and z are integers, and y+z=the valence of the metal, and (ii) a sulfur compound of the group consisting of alkyl and aryl xanthates, alkyl and aryl thiuram sulfides (including thiuram disulfides), thiourea, alkyland aryl-substituted thiourea, thioamides (including thiooxarnide) and alkyland arylsubstituted thioamides (including thiooxamides). Heat sensitive compositions according to the invention are prepared by dispersing such a reaction product in a film forming binder, such for example as a vinyl or styrene polymer or a cyclized rubber dissolved in a solvent. Thermographic copying sheets are prepared by coating such composition on a suitable support such as paper or film which is substantially transparent to infra-red radiation.

The single figure of the accompanying'drawing shows schematically, in cross-section, a thermographic copying sheet comprising an infra-red transparent paper base and a heat-sensitive coating of the character herein described.

Following are type formulae of which are believed to be the-reaction products which render composition according to the invention heat-sensitive. While these type formulae are believed to represent correctly the reaction products involved, the invention is not dependent on their accuracy, and they are not to be considered as limiting the scope or" the invention.

A. N-alkylation reaction product of an alkyl or aryl {bismuth compound with thiourea or an alkyl or arylsubstituted tliiourea:

were R and R may be alkyl or aryl groups, and R and R may be hydrogen or an alkyl or aryl group.

Patented Apr. 13, 1965 3 B. 'S-alkylation reaction product of an alkyl or aryl mercury compound with an alkylor aryl-substituted thiourea:

where R, R and R and R may be alkyl or aryl.

C. Reaction product of an alkyl or aryl lead compound with an alkyl or aryl xanthate:

( 1)a b-S Where R and R may be alkyl or aryl.

D. Di-N-alkylation reaction product of an alkyl or aryl mercury compound with arylor alkyl-substitu-ted thicurea:

where R, R R and R may be alkyl or aryl.

E. Reaction product of alkyl or aryl lead compound with an alkyl thiouram disu'lfide:

(R1)glb-S Where R and R may be alkyl or aryl.

Reaction product of an alkyl or a-ryl germanium compound with a thioamide:

/R1 (R)3GGN where R may be alkyl or aryl and R and R may be hydrogen, alkyl or :aryl.

Following are specific examples of heat-sensitive compositions according to the invention, and of their application to a paper support sheet to form a thermographic copying sheet:

Example 1 Phenyl mercuric benzoate g 3 Di-N-octyl thiourea g 1 Polyvinylacetate 'g 1 Methanol ml The phenyl mercuric benzoate and di-N-octyl thiourea in the proportion stated were reacted in the methanol for three hours, the polyvinyl-acetate was added under agitation and the mixture was then ball-milled to insure breaking up of all solid lumps and to reduce the reaction product to a good coating consistency. It was then coated on a standard type of paper having good infra-red transmissibility for thermogra'phic reproduction. When exposed in contact with a printed test sheet in a conventional lthermographic copying machine, the coated paper yielded a fine black on white reproduction of the .test sheet.

In each 'of the following Examples 2 to 13, the reagents specified were reacted in the proportion stated and ballmilled, in the same manner as in Example 1. The resulting composition was (in each case coated on a suitable paper and found to produce thereby a thermographic copying sheet on which a fine reproduction of a printed test sheet could be made in a conventional thermographic copying machine.

Example 2 Triphenyl germanium chloride granrsu 4.0 Di-ethyltthioura dO 1.5 Cyclized natural rubber (#Pliolite NR) do 1.5 Toluene ml 10 Example 3 Diethylt-in dichloride grams 2.5 Ethylenethiourea d0 1.3 Cyclized natural rubber PLiOIite NR) d0 1 Toluene ml 10 Example 4 Methyl gallium dichloride "grams" 4.0 Di-n butylthiourea "10---- 1.5 Styrene copolymer resin (Piccotex) d0 2 Heptane ml 15 Example 5 Phenyl mercuric tosylate grams 4.5 Diphenylthiocarbanilide d0 1.5 Polyvinyl alcohol d0 2.0 Methanol ml 12 Example 6 Ethylmercuric hydroxide "grams" 3.0 Die-thylthiourea d0 1.5 Polyvinyl-formal-phenol formaldehyde resin in cres slic acid solution (*Formvar) grams 2.0 Methanol ml 10 Example 7 Dimethyltelluronium dichloride grarns 4.0 Thiourea d0 1.0 Polyvinyl acetate d0 1.0 Methanol ml 10 Water ml 1.0

Example 8 Phenyl mercuric nitrate grarns 6.0 Potassium sec-amylxanthate do 3.0 Polyvinyl pyrrolidone do 1.0 Methanol ml 12 Water ml 2.0

Example 9 Trimethylgallium monoamine grams 4.0 Tetramethyl thiuram disulfide d0 3.0 Styrene copolymer resin (Piccotex) do 2.0 Ligroin ml 15 Example 10 Phenyl mercuric hydroxide grams 6.0 Dithiooxamide do 3.0 Carboxymethylcellulose do 1.0 Methanol ml 12 Water ml 1.2

Example 11 Triphenyl germanium bromide grams 8.0 Sodium dimethyldithiocarbamate do 2.0 Cyclized natural rubber (Pliolite NR) do 1.0 Toluene ml 20 Example 12 Naphthyl mercury stearate i grams 5.0 Thiourea "do"..- 1.0 Polyvinyl acetate in hexane (Gelva H) ml 15 Example 13 Di-o-tolyltin dichloride grams 4.5 Thiourea d0 1.5 Cyclized natural rubber (Pliolite NR) do 1.5

7 Heptane ml 10 I claim:

1. A heat-sensitive sheet comprising a base sheet carrying a coating of a heat-sensitive composition comprising a film+forming binder in which there is dispersed the reaction product of (i) a Grignard-type organometallic compound having the structure (R) M(X) in which R- is a substitutent selected from the group consisting of aryl and alkyl radicals, M is a metal of the group consisting of bismuth, chromium, gallium, germanium, iron, lead, mercury, tellurium and tin, X is an anion substituent, y and z each is an integer and y+z=the valence of the metal, and (ii) a sulfur compound of the group consisting of alkyl and aryl Xanthates, alkyl and aryl thiuram sulfides, thiourea, alkyl and aryl substituted thiourea, thioamides, and alkyl and aryl substituted thioamides.

2. A heat sensitive sheet according to claim 1, in which the heat-sensitive composition comprises the reaction product of a Grignard-type mercury compound.

3. A heat-sensitive sheet according to claim 1, in which the heat-sensitive composition comprises the reaction product of a phenyl mercuric compound.

4. A heat-sensitive sheet according to claim 1, in which the heat-sensitive composition comprises the reaction product of a Grignard-type gallium compound.

5. A heat-sensitive sheet according to claim 1, in which a heat-sensitive composition comprises the reaction product of a Grignard-type tin compound.

6. A heat-sensitive sheet according to claim 1, in which the heat-sensitive composition comprises the reaction product of thiourea.

7. A heat-sensitive sheet according to claim 1, in which the heat-sensitive composition comprises the reaction product of an alkyl substituted thiourea.

8. A heat-sensitive sheet according to claim 1, in which the heat-sensitive composition comprises the reaction product of a thioamide.

9. A heat-sensitive sheet according to claim 1, in which the heat-sensitive composition comprises the reaction product of a xanthate.

10. A heat-sensitive sheet according to claim 1, in which the heat-sensitive composition comprises the reaction product of a thiuram sulfide.

11. A heat-sensitive sheet according to claim 1, in which the heat-sensitive composition comprises the reaction product of a mercury compound and thiourea.

12. A heat-sensitive sheet according to claim 1, in which the heat-sensitive composition comprises the reaction product of a Grignard-type mercury compound and an alkyl substituted thiourea.

13. A heat-sensitive sheet according to claim 1, in

which the heat-sensitive composition comprises the reaction product of a phenyl mercuric compound and thiourea.

14. A heat-sensitive sheet according to claim 1, in which the heat-sensitive composition comprises the reaction product of a phenyl mercuric compound and an alkyl substituted thiourea.

15. A thermographic copying sheet comprising a base sheet of material which is substantially transparent to infra-red radiation, said sheet carrying a coating of a heat-sensitive composition comprising a film-forming binder in which there is dispersed the reaction product of (i) a Grignard-type organometallic compound having the structure (R) M-(X) in which R is a substituent selected from the group consisting of aryl and alkyl radicals, M is a metal of the group consisting of bismuth, chromium, gallium, germanium, iron, lead, mercury, tellurium and tin, X is an anion substituent, y and 1 each is an integer and y+z the valence of the metal, and (ii) a sulfur compound of the group consisting of alkyl and aryl Xanthates, alkyl and aryl thiuram sulfides, thiourea, alkyl and aryl substituted thiourea, thioamides, and alkyl and aryl substituted thioamides.

16. A heat-sensitive composition comprising a filmforming binder in which there is dispersed the reaction product of (i) a Grignard-type organometallic compound having the structure (R)y--M(X) in which R is a substituent selected from the group consisting of aryl and alkyl radicals, M is a metal of the group consisting of bismuth, chromium, gallium, germanium, iron, lead, mercury, tellurium and tin, X is an anion substituent, y and z each is an integer, and y+z=the valence of the metal, and (ii) a sulfur compound of the group consisting of alkyl and aryl Xanthates, alkyl and aryl thiuram sulfides, thiourea, alkyl and aryl substituted thiourea, thioamides, and alkyl and aryl substituted thioamides.

References Cited by the Examiner UNITED STATES PATENTS 1,844,199 2/32 Bicknell et 2.1. 1,880,449 10/32 Hickman et al. 2,095,839 10/37 Sheppard. 2,414,839 1/47 Schoen. 2,625,494 1/53 Morrison. 2,813,042 11/57 Gordon et al 11736.8 2,999,035 9/61 Sahler 11736.8

RICHARD D. NEVIUS, Primary Examiner.

MURRAY KATZ, Examiner, 

1. A HEAT-SENSITIVE SHEET COMPRISING A BASE SHEET CARRYING A COATING OF A HEAT-SENSITIVE COMPOSITION COMPRISING A FILM-FORMING BINDER IN WHICH THERE IS DISPERSED THE REACTION PRODUCT OF (I) A GRIGNARD-TYPE ORGANOMETALLIC COMPOUND HAVING THE STRUCTURE (R)Y-M-(X)Z, IN WHICH R IS A SUBSTITUTENT SELECTED FROM THE GROUP CONSISTING OF ARYL AND ALKYL RADICALS, M IS A METAL OF THE GROUP CONSISTING OF BISMUTH, CHROMIUM, GALLIUM, GERMANIUM, IRON, LEAD, MERCURY, TELLURIUM AND TIN, X IS AN ANION SUBSTITUENT, Y AND Z EACH IS AN INTEGER AND Y+Z=THE VALENCE OF THE METAL, AND (II) A SULFUR COMPOUND OF THE GROUP CONSISTING OF ALKYL AND ARYL XANTHATES, ALKYL AND ARYL THIURAM SULFIDES, THIUREA, ALKYL AND ARYL SUBSTITUTED THIOUREA, THIOAMIDES, AND ALKYL AND ARYL SUBSTITUTED THIOAMIDES. 